The automation of immunoassay techniques which have well defined specifications has spawned a series of improvements making the automation of such processes possible. A series of applications assigned to a common assignee covering these devices and methods have been filed July 22, 1985 under the titles METHOD AND APPARATUS FOR PERFORMING AUTOMATED, MULTI-SEQUENTIAL IMMUNOASSAYS U.S. Pat. No. 4,816,418, TUBE TRAP APPARATUS, U.S. Pat. No. 4,713,218, PROBE WASH STATION U.S. Pat. No. 4,730,631, and, METHOD AND APPARATUS FOR REMOVING UNBOUND COMPONENTS IN AUTOMATED IMMUNOASSAY TECHNIQUES U.S. Pat. No. 4,803,050, and PULSE EDITING APPARATUS AND METHOD now abandoned. The relevant portions of these applications are hereby incorporated by reference into this application.
The problem to which this particular invention is addressed concerns the addition of a diluent and/or a quenching reagent to a reaction solution before the solution is measured in an optical reader to obtain absorbance or fluorescence measurements. To be able to run several racks of assays sequentially, no one rack must occupy the instrument for too long a period. Accommodating the necessary mixing and reaction times inherent to the immunoassay techniques proves difficult in view of cycle time limitations. In the steps of the technique following incubation of the sample, solid support and conjugate, the solid support is washed to remove traces of unbound antibody and conjugate reagents and a substrate reagent is added. Subsequently, after another incubation period a diluent and/or a quenching reagent are added to the reaction tube to obtain an optically detectable substance. The addition of these liquids to the washed solid support must be made in such a way that the solution is uniformly mixed to insure the accuracy and precision of the optical determination. When the addition of the diluent/quench is accomplished manually, the sample can be vigorously agitated and provided with extra time to accomplish uniform mixing. In the automated procedure, neither of these aspects of manual mixing were easily accommodated into the short cycle time made necessary by the automation of this procedure.
The subject invention provides for adding the diluent and/or quenching reagent to one row of reaction tubes through a reagent probe and offsetting by one row from the reagent probe the optic probe that simultaneously aspirates previously diluted quenched sample into the optical reading system. The simultaneous addition of the diluent/quench and the aspiration/optical reading can be accomplished in less than 17 seconds per sample so the addition of diluent/quench for a given row of five samples can be accomplished in 85 seconds. The offset of the diluent/quench and reading in successive rows provides 85 seconds for good mixing to occur between the addition of the diluent/quench reagents and the reading of the result. Furthermore, the probe dimensions are selected so that the diluent is added from a height above the eventual surface of the liquid in the reaction tube in a forceful manner to facilitate mixing. The movement of the rack in which the reaction tubes are stored also helps the mixing process.
It is therefore an object of this invention to provide reagent and optics module probes which are located on the same carriage.
It is a further object of this invention to provide sufficient mixing in an automated instrument for immunoassay techniques to provide a uniform solution for optical reading.
It is still a further object of this invention to provide for sufficient mixing to occur between the addition of the diluent/quench and the reading of the result in a short period of time, enabling the rapid throughput which is required for clinical applications of automated techniques.